Ash handling system for high-pressure combustion of pulverized solid fuels



Oct. 6; 1953 J. YELLOTT ASH HANDLING SYSTEM FOR HIGH-PRESSURE COMBUSTION0F PULVERIZED soun FUELS 2 Sheets-Sheet 1 Filed June 5, 1948 T INVENTOR.JZJHNZXELLUTT ATTUHZSZEY Oct. 6, 1953 J. YELLOTT ASH HANDLING SYSTEM FORHIGH-PRESSURE COMBUSTION OF PULVERIZED SOLID FUELS 2 Sheets-Shed 2 FiledJune 3, 1948 m 5 6 2 2 W 4 6 a w 0 v 4 w 5 z 4 w 4. M

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000000 GOO0,0 m 7 2 m I 2 07 z w 7 E m 2 r0 7 O 4 4 W m 7 m z a z y a m.2 7 6 I 0 0 2 2 I 1 4 I 1 1 1 I 'llIllIlIIIlIIIIIIIl/IlIIIIIIIIIIIIIIv, nunnnul Patented Oct. 6, 1953 ASH HANDLING SYSTEM FOR HIGH-PRES- SURECOMBUSTION OF PULVERIZED SOLID FUELS John I. Yellott, Cockeysville, Md.,assignor to Bituminous Coal Research, Inc., Washington, D. 0., acorporation of Delaware Application June 3, 1948, Serial No. 30,816Claims. (01. (so-39.46)

This invention relates to improvements in the pressurized combustion ofpulverulent solid fuels, and, more particularly to a novel system andapparatus for cooling and conveying hot fly-ash separated from thegaseous products of combustion of pulverulent fuel.

In my Patent No. 2,583,921 of January 29, 1952, I have shown and claimeda special pressurized combustion system, including novel means forseparating fly-ash from the gaseous products of combustion ofpulverulent fuel.

I have now found that the fiy-ash derived from the pressurizedcombustion of pulverulent fuel should be cooled as rapidly as possibleto a temperature below the ignition temperature of any uncombustedoversize fuel particles and of the unburned carbon which is commonlycontained in fly-ash.

It is, therefore, among the features of novelty and advantage of thepresent invention to provide a fiy-ash cooling and treating system whichwill permit the continuous removal of superheated fly-ash from a fly-ashseparator and discharge of the same in a pressurized stream ofrelatively cool air into a container, the coolant air with the heatunits derived from the now cooled fly-ash being returned to the systemas added motive gases, or discharged to the atmosphere, while the storedfiy-ash, being relatively cool, is not subject to burning or clinkering.

The features of novelty and advantage of the present invention whichhave been indicated hereinabove, will be more readily comprehended byreference to the following specification and accompanying drawings,wherein there is disclosed a generating electric power plant embody inga pulverized coal-fired gas turbine installation incorporating a novelfiy-ash separator, and in which like numerals refer to similar partsthroughout the several views, of which Fig. l is a perspective view of agenerating electric power plant embodying a gas turbine, a fly-ashseparator, coal-fired combustor, and a fly-ash cooling device;

Fig. 2 is a detail view, partlyin vertical section and partly inelevation, of the fly-ash separator and cooler showing theinter-connections therebetween;

Fig. 3 is a vertical section taken on line 33 of Fig. 2, showing thefly-ash discharge means from the bottom of the fly-ash separator, and

Fig. 4 is a horizontal section taken on lines 4-4 of Fig. 2, showing theinlet into the fly-ash cooler and separator.

In the gas turbine-generating electric power unit shown in Fig. l, andmore particularly claimed in my application Serial No. 746,818, filedMay 8, 1947, now Patent No. 2,583,921, issued January 29, 1952, thepower plant comprises a bed or base it! of spaced parallel evertedchannels I l, secured by interposed cross-bracing members, designatedgenerally by the numeral l2. When used in a locomotive, the bed may beintegral with the locomotive frame. The power unit comprises a gasturbine 20, an air compressor 60, and a generator coupled to the turbineshaft through gear box 10. Gas turbine 20 has an exhaust stack 2| inwhich is mounted a combustor 3B and two banks of regenerator tubes 49 oneither side of the combustor unit. A pair of inlet ducts 22, 23 connectthe turbine to a fly-ash separator I00. Separator m0 is secured betweenthe frame members H in any suitable manner. An air compressor 60 ismounted on the turbine shaft and discharges moderate pressure air of theorder of 60 to 100 p. s. 1. through ducts 5| into the combustor andregenerator tubes, as will be described more in detail hereinafter. Gearbox 10 serves to couple the turbo-compressor shaft to generator unit 80,mounting auxiliary generators 8|, 82 thereon. The auxiliary generator 8!serves to power auxiliary equipment, including a field generator orexciter 83 for the main generator 80. Auxiliary generator 82 is D. C.Wound and the same shaft powers the high pressure booster compressor 84.This booster compressor, or auxiliary air pump, is connected throughline 85 to the pressure or discharge side of compressor 60, as shown inFig. 1. Booster compressor 84 discharges through line 86 and a Tconnection to an auxiliary high pressure air tank 81, and a separatehigh pressure air line 88. The pressure tank 81 can also serve as areservoir for air-brake air, and for other equipment, such as bellringers, sanders, control equipment, and the like.

The coal utilized for combustion is fed from supply means, not shown, byhigh pressure air line 88, the streaming entrainment of fluidized solidparticles being delivered through line 89 and coal atomizer 90 to feedline 9| of combustor 30. A by-pass for the air-borne coal from feed line89 back to the storage hopper, not shown, is provided by line 92, whichis connected to the atomizer 90 through'two-way valve 93. Thisarrangement permits the discontinuance of the coal feed and, conversely,the initiation of the coal feed, as when the turbine is first beingstarted, after being initially supplied with gaseous or liquid fuel.

An aspirator 95 having a relatively large open chamber 96 is connectedto the tip or discharge end 91 of dump line 92, the discharge end beingpreferably reduced, aligned with, and discharging into line 98 throughthe aspirator 95, the other end of the line 98 discharging into thecrushed coal hopper, not shown. When; as in the case of an emergencystop, or when shutting down the engine at the end of a run, or for anyother reason (as indicated above), the fluidized solid fuel supply inhigh pressure line 89 is diverted. through the atomizer into line 92 byoperating valve lever 94, any excess temperature possessed by the coalcontained therein is reduced by contact with an striction 91 into line08. This operation effectu-..

.. is secured to the cover by machine screws, not

ally cools the heated pressurized, fluidized .pul-. verulent fuel masswhich has been previously heated by contact with the high pressureatomizing air. This discharged-pressure air, now reduced in pressure andeffectively cooled to atemperature below the dangerpointof spontaneouscombustion, with its "pulverulent coal, which forms a very finepowden'is discharged into the hopper (not shown) and prevented fromdischarging directly into the atmosphere.

Because of this novel safety feature, fire or explosion hazards in theoperation of the novel pressurized combustion system herein; are reducedbelow any danger point, even under conditions of shock such as canobtain in train wrecks and the like.

The combustor in its combination with' the compressor 60, turbine 20,exhaust stack 2|, re-

generator tube banks 40, and the fly-ash sep'ara' tor I00, is moreparticularly shown and claimed.

in my said Patent No. 2,583,921 andwill be described herein onlyinsuflicient detail to point out the novel elements of the systemforming the supply pipe 9!, which introduces'pulverized fuel into theflame tube in a pressurized, air-borne.

stream. The cap 36 is'provided further with a fluid fuel inlet tube 31for introducing liquid? or gaseous fuel for starting the turbine, and a.second fuel pipe 3 8 is provided for the introduction of a liquid orgaseous fuel to serve as. a pilot. light or.

igniter for the system. A sight tube 39 is also provided adjacent totheflame carrier, so as to. permit inspection thereof; For remote inspecetion and control, the sight tube may be provided with a suitable alarmsystem. A photoelectric cell, or other flame-and heat-responsivedevicemay be connected thereto, suitable connections. to the instrument boardof the system beingprovided.

The fuel delivered through coal atomizer 90 and feed pipe 9| to the.combustor 30, will becom busted therein and the products of. combustionwill be diluted in theupper mixing chamber of fly-ash separator I00 bythe extra, relatively cool air delivered through ducts of thecombustor-case ing and the air delivered through the tube sheets of theregenerator banks 40. The detailsof the novel fly-ash separator will bedescribed.

As shown in Fig. 2, the fly-ash separator. comprises a generallycylindrical, laminated pressure vessel I00, having an outer steel wall,an inner stainless steel heat-resistant lining, and any intermediate orinternal insulation filler between the At the fuel inlet'end the com-.

H0 in sliding bearing engagement.

-of" the same material as the bottom cover and 1-0- the wall of thecontainer. The cover H0 is centrally apertured to. receive shaft I Id ofpiston I I5, which, as shown, is mounted for reciprocation in cylinderH6 having a closed bottom with a central'boss centrally apertured toreceive the shaft The outer portion of the central boss is received in aconfer-med aperture in the cover I i0, and the cylinder shown, passingthrough the flanged base and into the top cover section. The upper endof the piston cylinder is closed by a removable plate I20,

secured in place by thev usual bolts and nuts, not.

shown. The piston H5 divides the pistoncylinder into an upper chamberand a lower chamber, which are severally connected to suitable sourcesof fluid supply by pipes I25,- I-26, respectively. A closure disc IZI,having a beveled seat is fixedly mounted on shaft H4. The disc I2? isadapted- .to be lifted up by the shaft IM when piston H5 is urgedupwardly by fluid pressure in the chamher 120. The function of theclosure disc I27 will be described more in detail hereinafter inconnection with the particular description of the separator tubeassembly.

An inlet chamber I30 connects the upper per-- tion of the cylinder I00with the combustor discharge and the regenerator discharge outlets.-

The inlet duct or passageway I30 is provided with ....parallel top andbottom walls I3I, I32 and outwardly flaring side walls, formed as a unitwith in'the wall of the container immediately below the duct I30 and aredisposed somewhat-below the middle of the vessel.

turbine byflexible. coupling members I31, I38.

Internally, the chamber or vessel I00 is divided into three sections:"an'upper' plenum chamber I50, a bottom fly-ash receiving chamber MI,and

an intermediate cleaned gas-receiving chamber IA'Lwhich discharges intothe outlets I35; I 30;

The plenum chamber and intermediate clean gas, receiving chamber,together with the fly-ash Claimed in my abovesaid Patent No; 2,583,921.

In the instantaneous burning of coal dust, a maximum rise of 3000? F.can occur. Since the normal operating temperature of the air in the.

inner chamber I41 will be about1300 F., or l760 abs, a rise intemperature of 3000" F. would pro.-

duce a total absolute temperature of 47.60 F. This is a three. to oneincrease in absolute tem-' perature, and, in a closed vessel,wouldresult in a pressure rise of three to' one. Because of the.unusually large venting area provided by the cyclone separators and theadjacent chambers the These ducts are severally connected to the inlets22', '23 of the gas inner chamber 5 M is instantaneously enlarged toinclude the upper chamber I40, the annular V trough immediately belowit, as well as the throat I30 leading from the combustor unit to theflyash separator, and the annular chamber I42, ducts I35, I36, and gasturbine 20. In other words, the quantity of intensely heated airdeveloped in the cylinder and resulting from the explosion, can beallowed to flow into a relatively large volume and certainly at leastthree times greater than that of the chamber, so that the force of theexplosion can be dissipated without resulting in harm to the equipment.

In a series of exhaustive studies on dust explosions the Bureau of Mineshas found that a venting area of 5 sq. ft. per hundred cubic feet ofexplosion volume affords an ample safety factor in closed chambers whereexplosion hazards exist. Because of the lack of venting space, suchconditions indicate positive explosion hazards. As the vent areaincreases up to 2 sq. ft. per hundred cubic feet of explosion volume, itwill be seen that the pressure developed, expressed in pounds per squarefoot, decreases, arriving asymptotically at a minimum value between 5and sq. ft. of venting area per 100 cubic feet of explosion volume.

Considering these controlling factors with respect to the inventionherein, the inherent safety factor will be apparent. The fiy-ash chamberI4! is in open communication with the upper plenum chamber I40 anditheducts 22, 23 leading to the turbine as well with the chambers formed bythe separator units I50 and their supporting structures. The separatorunits I50 provide free, substantially unimpeded paths between allchambers so that thefiy-ash chamber I4I has a vent area equal tosubstantially 70% of its surface which aifords a positive assurance ofsafety from explosions due to delayed combustion of solid combustivematerials in the fiy-ash chamber under high pressure conditions.

In the pressurized combustion system herein this type of safety factoris of maximum importance, as well as from the operating efilciency asfrom the primary and controlling factor of safe-guarding human life.Because of the relatively enormous vent area provided, the pressuresutilized can be greatly increased without increasing explosion dangersin a comparable manner. With any explosion in the fly-ash chamber, the

gase are vented immediately, in opposed directionsj through the turbineon one side, and back through the plenum chamber and combustor on theother side, 'softhat, the volume of discharge space available in theturbine and its inlet ducts and outlet exhaust stack,"as well as in theplenum and mixing chamber of the combustor, and the combustor itselftogether with the regenerator tubes, is extremely large as compared withthe restricted volume of the fly-ash chamber.

The special fly-ash disposal system for pressurized combustion systemsof the type shown in my said Patent No. 2,583,921, issued January 29,1952, for Multiple Element Vortical Whirl Ash Separator, and as showngenerally in Figs. 1 and 2, comprises a second, combination fiy-ashseparator and storage tank 200, feed line 2I0, cleaned air dischargesystem 220, and high pressure ejector feed line 230. To integrate thefly-ash separator of my above said application with the present system,the fly-ash receiving chamber MI is provided with a V-trough 24I,discharging through elbow 242 of ash dump line 243 into feed line 2l0. Aworm 244 is mounted for constant rotation in the V-trough MI and isdriven by motor 245, as shown in Fig. 2.

The second, combination fly-ash separator and storage tank 200 comprisesa generally cylindrical tank having a bodyportion 20I with a truncatedconical bottom 202 closed by a large dump valve, designated generally bythe numeral 203. In place of the dump valve, the tank may dischargethrough a depressurizer, permitting the ash to be stored at atmosphericpressure. The top of the tank is closed by annular plate 204 having anaxial discharge opening 205, and mounting a depending cylinder 206. Atangentia1 inlet 201 is formed in the upper cylinder wall immediatelybelow the cover plate 204.

The air feed line 2I0 is tapped into the discharge duct 6| of the maincompressor 60, and is brought to tank 200 after picking up fly-ashdischarged through dump line 243. Immediately upstream of the dump line243 the line 2"! is fitted with a reducing nozzle 2 II which serves toincrease the velocity of the pickup and coolant air flowing past thedischarge opening of dump line 243, and to equalize the pressure in thedischarge line. A valve M2 is mounted in the line 2I0 upstream of thenozzle to control the fiow of air therethrough. Normally, the flowthrough line 2! will be less than 1% of the total air flow. Downstreamof dump line 243 the air line 2I0 is directed upwardly, to form an ashdelivery line 2 I3, then horizontally to form tangential delivery line224, whose outlet is secured to, and is coextensive with inlet 20?, inthe tank 200. A valve 2 I 5 is fitted in line 2 I 3 upstream of theoutlet.

The cleaned air discharge system 220 comprises a vertical line 22isecured to discharg opening 225 of tank 20L The line 22I is directedhorizontally, as indicated at 222 to the inlet 223 of airoperatedejector 224. The ejector 224 discharges downwardly into line 225 fittedwith valve 220, the line being directed horizontally, below the valve asindicated at 221, into the plenum or mixing chamber I40 of the fiy-ashseparator I00.

The high pressure ejector feed line 230, is supplied with air fromauxiliary compressor 84, and isconnected at 23! to the inlet 223 ofejector nozzle 224. A valve 232 is fitted in line 230 and desirablyadjacent the discharge 23!. A twoway valve 228 and discharge pipe 229are provided in line 220 to vent the clean air from the tank 200 totheatmosphere or to auxiliary heating services, when it is not desired torecycle it to the fly-ash chamber.

The operation of the combination ash cooling and auxiliary motive gasgenerating system, de scribed immediately above, will be considered withrespecttir'tiieg nprovement in overall operation and efficiencyofcoal-burning gas-turbine power plants, and particularlytiof such powerplants as incorporated in locomotives, aiidmarine installations.

Motive gases are delivered from fly-ash separator I00 to gas turbine 20at maximum operating temperatures of 1300 F., to 1350 F. At thesetemperatures, the separated fly-ash, which is discharged and collectedin fiy-ash receiving chamber I4I, retains significant quantities ofheat. The ash, having a low heat conductivity, is essentially a goodinsulating material. Because of the poor heat transfer characteristicsof the ash, the problem of cooling superheated (1300 F.) masses of thesame, in restricted spaces, as in locomotives and marine installations,where space is always at a premium, assumes major engineeringimportance. This problem is complicated further by the fact that thesystem must be maintained pressurized, and, in the instant system,desirably at an operating pressure of 4-5 atmospheres at the turbineinlets. The novel ashcooling system herein solves this problem bycooling the hot (1300 F.) ash in an, ejector stream of coolant gaseousfluid (air, steam, etc), and discharging it into a cyclone separatorwhere it undergoes further cooling and separation from the gaseousentraining stream.

What is claimed is:

1. In a plant for the pressurized combustion of pulverized fuel, acombustion chamber, a discharge line for the products of combustion,means in said discharge line effective to remove the flyash from theproducts of combustion comprising a first ash separator, a second ashseparator, pneumatic conduit means connecting the ash discharge of thefirst said separato to the inlet of the second said separator, means fordischarging ash from the first separator into the said pneumaticconduit, and means for delivering pneumatic coolant through said conduitto the second said separator, whereby entrained ash from the firstseparator is cooled and delivered to the second separator and the cooledash is separated from the entraining fluid.

2. System according to claim 1 in which the second said separatorincorporates a storage chamber.

3. In a power plant for the pressurized combustion of pulverized fuel,in combination, a combustion chamber, a discharge line for the productsof combustion, a first ash separator in said discharge line to removethe ash from the products of combustion, means for cooling saidseparated ash to remove the heat energy therefrom, means to return tothe system the heat energy derived from the-separated ash, said meansincluding a second separator incorporating ash storage means and acleaned air return line to the system.

4. System according to claim 3 in which the clean gas discharge linefrom the second separator is connected to the input side of the firstsaid ash separator.

5. In an apparatus for the pressurized burning of pulverized fuel havinga combustion chamber, a discharge line for the products of combustion, afly-ash separator, and a fiy-ash receiving chamber in the separator, theimprovements comprising fly-ash discharge means in the said chamber, andefferent pneumatic conduit means connected to the said chamber dischargemeans, whereby the discharged hot ash from the separator isentrained andcooled in said pneumatic conduit.

JOHN I. YELLOTT.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 730,782 Morrison June 9, 1903 1,814,560 Kreisinger July 14,1931 2,055,385 Noack Sept. 22, 1936 2,187,627 Noack Jan. 16, 19402,192,885 Avery Mar. 12, 1940 2,288,734 Noack July 7, 1942 2,375,436Noack May 8, 1945 2,399,884 Noack May '7, 1946 2,401,285 Woodward May28, 1946 2,445,388 Ramseyer Aug. 3, 1948 2,509,246 Ramsey May 30, 1950FOREIGN PATENTS Number Country Date 168,406 Great Britain Aug. 31, 1921

